In rotary equipment such as kilns, driers, coolers, mills, trommels, etc. it is desirable to seal the internal hollow part of the equipment from the surrounding atmosphere. For example, in kilns there are often generated substantial amounts of heat and gases which could escape to the surrounding atmosphere if a seal about the rotary kiln were not provided. However, sealing rotary devices are characterized by some rather unique problems relating to countervailing considerations of rotation and sealing, since sealing usually is accompanied by a need for increased friction while rotation should have reduced friction. Thus, in providing the seal for a rotary kiln it is necessary to preferably enhance and at least not detract from rotation of the device due to friction imparted by the sealing mechanism.
Seals for such purposes have been provided before in the prior art, but these have been relatively complex in construction and operation. This complexity has raised the cost of initial construction as well as maintenance due to the difficulty in replacing seals. In addition, seals available heretofore have not been adjustable for dimensional variations in the periphery of the rotary equipment due to expansion and contraction from temperature changes, wear of the various elements, or runout of the rotary element.
The subject invention overcomes the problems which have constantly impaired the sealing mechanism for rotary equipment and particularly for equipment subjected to hot gases. Generally, the invention includes a plurality of graphite block segments circumscribing the periphery of the rotating element, for example a kiln, whereby the block segments are gently pressed against the shell by seal adjusting segments. Pressure is applied by the hoop tension generated by counterweighted rope wound completely around these segments. In this way the graphite block segments are biased against the peripheral surface of the rotating element while simultaneously accommodating changes in the surface of the kiln. For example, when the rotating element expands due to the increase in temperature, the graphite blocks will be moved radially outwardly against the hoop tension provided by the counterweighted rope. Conversely, during the cooling process where the drum will contract, the graphite blocks will move radially inwardly under the pressure, i.e. hoop tension, provided by the counterweighted rope to maintain the blocks continuously in contact with the outer surface of the rotatin kiln.
The use of a plurality of segments described above in conjunction with a specially configured holding mechanism facilitates replacement of individual segments without having to diassemble the entire sealing mechanism. Adjacent the area to be sealed, there is provided an outer stationary ring and an inner stationary ring spaced laterally apart from one another and circumscribing the periphery of the rotary kiln. Spacers fixed between the inner and outer rings maintain the desired space relationship while also providing for radial movement of the graphite blocks and holder segments carried between the spaced rings. The holder segments are slotted radially, and a bolt is passed through the slot and fixed to each of the rings. In this way the holder segment is maintained for radial movement, but prevented from lateral movement during rotation of the rotary kiln, to accommodate changes in the surface configuration of the kiln in the radial direction. The bottom portion of these segments is configured to restrain the graphite blocks from circumferential movement and for this purpose include extensions to grasp the graphite blocks on either end. When it is desired to replace one of these graphite blocks due to wear or damage, the bolt can simply be removed allowing initially the holder segment and subsequently the graphite block to be readily removed without interfering with the construction or placement of the other segments and blocks. A new segment and block are then bolted into place and the operation of the rotary equipment continued.
The sealing system of segments and blocks described above can be used with both the feed and discharge chutes. In addition, except for nominal leakage, this system can be applied to prevent either infiltration of outside air into the drum or escape of gases from within the drum depending on positive or negative pressure generation during operation of the kiln.
With the above construction sealing of the rotating equipment is accomplished simply and yet efficiently to maintain the seal between the surrounding atmosphere and the internal portions of the drum while providing easy replacement of the various segments without having to disassemble the entire mechanism. Furthermore, the graphite block can shift position to compensate for wear of the blocks and changes of the surface configuration of the rotating drum.